Methods that analyze the strength of connections between users in social network services or the prediction of users' preferences regarding products in online shopping as matters of the structure of a network and the link strength thereof have been proposed. Non-Patent Literature 1 proposes an analytical method that simultaneously performs link prediction on a plurality of types of links between nodes in a network.
Further, Non-Patent Literature 2 proposes a flexible analytical method that expresses to what extent structural differences described above exist between networks as a probability model. As an application of this analytical method, data of different product categories available online are simultaneously analyzed, and the results indicate that the method is capable of predicting users' preferences more accurately than when each data of individual product categories are separately analyzed.
Non-Patent Literatures 3 and 4 are reference documents regarding hierarchical models.